Global Styles: allow read access to users with edit_posts capabilities

[ramonopoly]

This ticket tracks the syncing of the Gutenberg PR:

​Global Styles: allow read access to users with edit_posts capabilities

The gist is to allow any role that can edit a post, including custom post types, to read global styles from the API and in the editor.

Why?

Block style variations and other global styles are not available to non-admin editors. See: ​https://github.com/WordPress/gutenberg/issues/64755

Furthermore, having global styles available in the post editor will, one day, allow block controls to reflect any values inherited from the theme/global styles. See: ​https://github.com/WordPress/gutenberg/issues/64670

In progress.

Syncing with ​https://github.com/WordPress/gutenberg/pull/65071

Trac ticket: https://core.trac.wordpress.org/ticket/62042

[spacedmonkey]

Marking as duplicate of #54516

I really don’t like making this data more accessible than it was before. This imo is like exposing data. Also this change means we would make it hardest in the future to add custom permissions to this endpoint.

Let’s move the discussion to #54516 cc @peterwilsoncc @TimothyBlynJacobs

[peterwilsoncc]

@spacedmonkey I'm not sure this is entirely a duplicate of the earlier issue. The earlier issue was to cover read and write capabilities, whereas this is exclusively about read permissions.

If custom styles are not reflected in the editor because post editors can't read them then I think, yes, they ought to be available for read access by post editors. If that's the case, they will need to consider further instances such as when an auhtor can edit custom post types using custom capabilities.

[ramonopoly]

whereas this is exclusively about read permissions.

Thanks @peterwilsoncc

Yes, it's strictly about read access in the editor, so folks who already have edit posts capabilities.

I understand there's a larger scope regarding permissions for the post type in general, and also that there are nuances about permissions that the proposed PRs might have missed, so any constructive feedback is very welcome.

I'll reopen for now pending further discussion.

[peterwilsoncc]

I've moved this to the milestone and reclassified it as a bug fix for the upstream ticket ​GB#64755.

[ramonopoly]

In 59048:

Global Styles: allow read access to users with edit_posts capabilities

This patch any role that can edit a post, including custom post types, or edit theme options to read global styles from the API. This enables read-only access to global styles in the post editor. Test coverage in included.

Props ramonopoly, peterwilsoncc, mukesh27, aaronrobertshaw, mamaduka, spacedmonkey, talldanwp, timothyblynjacobs.
Fixes #62042.

Committed in r59048 / 52d46a9cb3d808340f2d7b35a0120354bf8ecaf2